The use of semiconductor light modulators is gaining in popularity as a replacement for the laser polygon scanner in xerographic printing processes. A technology of preference, due to its monolithic, semiconductor fabrication process, is the deformable mirror device (DMD). U.S. Pat. No. 5,041,851, issued Aug. 20, 1991, entitled "Spatial Light Modulator Printer and Method of Operation," assigned to the common assignee with this patent application, which patent is hereby incorporated by reference herein, discusses one embodiment of a DMD device using a tungsten light focused via optics on a DMD array. While the invention in that application functions very well, several areas of improvement have become apparent.
All xerographic printing systems, especially laser systems, suffer from the problem that there are a large number of parts which must be assembled in order to make the process operate properly. In addition to the light modulation system (which contains a number of parts which must be in perfect optical alignment) there is the xerographic drum, the toner delivery system, the developer system, the paper handling system and the fuser system. Systems that use print engines include fax machines and copiers, each which include additional components. Each of these systems have many internal parts which must be accurately assembled and, in addition, all of the systems must be aligned with each other, and remain in alignment for the life of the product.
Thus, in addition to the cost of manufacturing each system, there is the additional cost of assembling each of the systems into the final product. A part of this cost involves the cost of aligning the optical path from the light source, through the modulator to the drum. Compounding the problem is the fact that essentially all of the systems wear out or require adjustment from time to time and therefore can be easily replaced without interfering with, or requiring adjustment to, the optical alignment, or the remaining xerographic components.
Accordingly, there is a need in the art for a printing system in which the xerographic reproduction mechanism can be manufactured with a minimum of parts and where the system elements prone to wear with use are either extremely reliable and long lived, or can be replaced easily while still maintaining both physical and optical alignment.
There is a need in the art for such a system in which the various component can be embedded into a compact system in order to reduce to a minimum the printer system size, while maintaining high reliability and ease of serviceability. The various additional components could be such things as copier interfaces, document scanners and the like, make the printer usable also as a fax machine, document scanner or copier.